Contents

The concept "cradle of civilization" is the subject of much debate. The figurative use of cradle to mean "the place or region in which anything is nurtured or sheltered in its earlier stage" is traced by the Oxford English Dictionary to Spenser (1590). Charles Rollin's Ancient History (1734) has "Egypt that served at first as the cradle of the holy nation".

The earliest signs of a process leading to sedentary culture can be seen in the Levant to as early as 12,000 BC, when the Natufian culture became sedentary; it evolved into an agricultural society by 10,000 BC.[10] The importance of water to safeguard an abundant and stable food supply, due to favourable conditions for hunting, fishing and gathering resources including cereals, provided an initial wide spectrum economy that triggered the creation of permanent villages.[11]

In the absence of written documents, most aspects of the rise of early civilizations are contained in archaeological assessments that document the development of formal institutions and the material culture. A "civilized" way of life is ultimately linked to conditions coming almost exclusively from intensive agriculture. Gordon Childe defined the development of civilization as the result of two successive revolutions: the Neolithic Revolution, triggering the development of settled communities, and the Urban Revolution, which enhanced tendencies towards dense settlements, specialized occupational groups, social classes, exploitation of surpluses, monumental public buildings and writing. Few of those conditions, however, are unchallenged by the records: dense settlements were not attested in Egypt's Old Kingdom and were absent in the Maya area;[citation needed] the Incas lacked writing altogether; and often monumental architecture preceded any indication of village settlement. For instance, in present-day Louisiana, researchers have determined that cultures that were primarily nomadic organized over generations to build earthwork mounds at seasonal settlements as early as 3400 BC. Rather than a succession of events and preconditions, the rise of civilization could equally be hypothesized as an accelerated process that started with incipient agriculture and culminated in the Oriental Bronze Age.[13]

A traditional theory of the spread of civilization is that it began in the Fertile Crescent and spread out from there by influence.[14] Scholars more generally now believe that civilizations arose independently at several locations in both hemispheres. They have observed that sociocultural developments occurred along different timeframes. "Sedentary" and "nomadic" communities continued to interact considerably; they were not strictly divided among widely different cultural groups. The concept of a cradle of civilization has a focus where the inhabitants came to build cities, to create writing systems, to experiment in techniques for making pottery and using metals, to domesticate animals, and to develop complex social structures involving class systems.[5]

Around 10,200 BC the first fully developed Neolithic cultures belonging to the phases Pre-Pottery Neolithic A (PPNA) and Pre-Pottery Neolithic B (7600 to 6000 BC) appeared in the fertile crescent and from there spread eastwards and westwards.[23] One of the most notable PPNA settlements is Jericho in the Levant region, thought to be the world's first town (settled around 8500 BC and fortified around 6800 BC).[24][25] In Mesopotamia, the convergence of the Tigris and Euphrates rivers produced rich fertile soil and a supply of water for irrigation. The civilizations that emerged around these rivers are among the earliest known non-nomadic agrarian societies. It is because of this that the fertile crescent region, and Mesopotamia in particular, are often referred to as the cradle of civilization.[26] The period known as the Ubaid period (c. 6500 to 3800 BC) is the earliest known period on the alluvial plain, although it is likely earlier periods exist obscured under the alluvium.[27][28] It was during the Ubaid period that the movement towards urbanization began. Agriculture and animal husbandry were widely practiced in sedentary communities, particularly in Northern Mesopotamia, and intensive irrigated hydraulic agriculture began to be practiced in the south.[29] Around 6000 BC, Neolithic settlements appear all over Egypt.[30] Studies based on morphological,[31]genetic,[32][33][34][35][36] and archaeological data[37][38][39][40] have attributed these settlements to migrants from the Fertile Crescent in the Near East returning during the Egyptian and North African Neolithic, bringing agriculture to the region. Eridu is the oldest Sumerian site settled during this period, around 5300 BC, and the city of Ur also first dates to the end of this period.[41] In the south, the Ubaid period had a very long duration from around 6500 to 3800 BC; when it is replaced by the Uruk period.[42]

Sumerian civilization coalesces in the subsequent Uruk period (4000 to 3100 BC).[43] Named after the Sumerian city of Uruk, this period saw the emergence of urban life in Mesopotamia and, during its later phase, the gradual emergence of the cuneiform script. Proto-writing in the region dates to around 3500 BC, with the earliest texts dating to 3300 BC; early cuneiform writing emerged in 3000 BC.[44] It was also during this period that pottery painting declined as copper started to become popular, along with cylinder seals.[45] Sumerian cities during the Uruk period were probably theocratic and were most likely headed by a priest-king (ensi), assisted by a council of elders, including both men and women.[46] It is quite possible that the later Sumerian pantheon was modeled upon this political structure. Uruk trade networks started to expand to other parts of Mesopotamia and as far as North Caucasus, and strong signs of governmental organization and social stratification began to emerge leading to the Early Dynastic Period (c. 2900 BC).[47][48][49] The Jemdet Nasr period, which is generally dated from 3100–2900 BC and succeeds the Uruk period, is known as one of the formative stages in the development of the cuneiform script. The oldest clay tablets come from Uruk and date to the late fourth millennium BC, slightly earlier than the Jemdet Nasr Period. By the time of the Jemdet Nasr Period, the script had already undergone a number of significant changes. It originally consisted of pictographs, but by the time of the Jemdet Nasr Period it was already adopting simpler and more abstract designs. It is also during this period that the script acquired its iconic wedge-shaped appearance.[50] At the end of the Jemdet Nasr period there was a major archaeologically attested river flood in Shuruppak and other parts of Mesopotamia. Polychrome pottery from a destruction level below the flood deposit has been dated to immediately before the Early Dynastic Period around 2900 BC.[51][52]

After the Early Dynastic period begins, there was a shift in control of the city-states from the temple establishment headed by council of elders led by a priestly "En" (a male figure when it was a temple for a goddess, or a female figure when headed by a male god)[53] towards a more secular Lugal (Lu = man, Gal = great) and includes such legendary patriarchal figures as Enmerkar, Lugalbanda and Gilgamesh—who are supposed to have reigned shortly before the historic record opens c. 2700 BC, when the now deciphered syllabic writing started to develop from the early pictograms. The center of Sumerian culture remained in southern Mesopotamia, even though rulers soon began expanding into neighboring areas, and neighboring Semitic groups adopted much of Sumerian culture for their own. The earliest ziggurats began near the end of the Early Dynastic Period, although architectural precursors in the form of raised platforms date back to the Ubaid period,.[54] The well-known Sumerian King List dates to the early second millennium BC. It consists of a succession of royal dynasties from different Sumerian cities, ranging back into the Early Dynastic Period. Each dynasty rises to prominence and dominates the region, only to be replaced by the next. The document was used by later Mesopotamian kings to legitimize their rule. While some of the information in the list can be checked against other texts such as economic documents, much of it is probably purely fictional, and its use as a historical document is limited.[49]

Eannatum, the Sumerian king of Lagash, established one of the first verifiable empires in history in 2500 BC.[55] The neighboring Elam, in modern Iran, was also part of the early urbanization during the Chalcolithic period.[56] Elamite states were among the leading political forces of the Ancient Near East.[57] The emergence of Elamite written records from around 3000 BC also parallels Sumerian history, where slightly earlier records have been found.[58][59] During the 3rd millennium BC, there developed a very intimate cultural symbiosis between the Sumerians and the Akkadians.[60]Akkadian gradually replaced Sumerian as a spoken language somewhere between the 3rd and the 2nd millennia BC.[61] The Semitic-speaking Akkadian empire emerged around 2350 BC under Sargon the Great.[47] The Akkadian Empire reached its political peak between the 24th and 22nd centuries BC. Under Sargon and his successors, the Akkadian language was briefly imposed on neighboring conquered states such as Elam and Gutium. After the fall of the Akkadian Empire and the overthrow of the Gutians, there was a brief reassertion of Sumerian dominance in Mesopotamia under the Third Dynasty of Ur.[62] After the final collapse of Sumerian hegemony in Mesootamia around 2004 BC, the Semitic Akkadian people of Mesopotamia eventually coalesced into two major Akkadian-speaking nations: Assyria in the north, and, a few centuries later, Babylonia in the south.[63][63][64]

The Indus Valley Civilisation starts around 3300 BC with what is referred to as the Early Harappan Phase (3300 to 2600 BC). The earliest examples of the Indus Script date to this period,[75][76] as well as the emergence of citadels representing centralised authority and an increasingly urban quality of life.[77] Trade networks linked this culture with related regional cultures and distant sources of raw materials, including lapis lazuli and other materials for bead-making. By this time, villagers had domesticated numerous crops, including peas, sesame seeds, dates, and cotton, as well as animals, including the water buffalo.[78][79]

2600 BC marks the Mature Harappan Phase during which Early Harappan communities turned into large urban centres including Harappa, Dholavira, Mohenjo-Daro, Lothal, Rupar, and Rakhigarhi, and more than 1,000 towns and villages, often of relatively small size.[80] Mature Harappans evolved new techniques in metallurgy and produced copper, bronze, lead, and tin and displayed advanced levels of engineering.[81] As seen in Harappa, Mohenjo-daro and the recently partially excavated Rakhigarhi, this urban plan included the world's first known urban sanitation systems: see hydraulic engineering of the Indus Valley Civilisation. Within the city, individual homes or groups of homes obtained water from wells. From a room that appears to have been set aside for bathing, waste water was directed to covered drains, which lined the major streets. Houses opened only to inner courtyards and smaller lanes. The house-building in some villages in the region still resembles in some respects the house-building of the Harappans.[82] The advanced architecture of the Harappans is shown by their impressive dockyards, granaries, warehouses, brick platforms, and protective walls. The massive walls of Indus cities most likely protected the Harappans from floods and may have dissuaded military conflicts.[83]

The people of the Indus Civilisation achieved great accuracy in measuring length, mass, and time. They were among the first to develop a system of uniform weights and measures. A comparison of available objects indicates large scale variation across the Indus territories. Their smallest division, which is marked on an ivory scale found in Lothal in Gujarat, was approximately 1.704 mm, the smallest division ever recorded on a scale of the Bronze Age. Harappan engineers followed the decimal division of measurement for all practical purposes, including the measurement of mass as revealed by their hexahedron weights.[84] These chert weights were in a ratio of 5:2:1 with weights of 0.05, 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, and 500 units, with each unit weighing approximately 28 grams, similar to the English Imperial ounce or Greek uncia, and smaller objects were weighed in similar ratios with the units of 0.871. However, as in other cultures, actual weights were not uniform throughout the area. The weights and measures later used in Kautilya's Arthashastra (4th century BC) are the same as those used in Lothal.[85]

Around 1800 BC, signs of a gradual decline began to emerge, and by around 1700 BC most of the cities had been abandoned.Suggested contributory causes for the localisation of the IVC include changes in the course of the river,[86] and climate change that is also signalled for the neighbouring areas of the Middle East.[87][88] As of 2016[update] many scholars believe that drought lead to a decline in trade with Egypt and Mesopotamia contributing to the collapse of the Indus Civilisation.[89] The Ghaggar-Hakra system was rain-fed,[90][91][note 1][92][note 2] and water-supply depended on the monsoons. The Indus Valley climate grew significantly cooler and drier from about 1800 BC, linked to a general weakening of the monsoon at that time.[90] The Indian monsoon declined and aridity increased, with the Ghaggar-Hakra retracting its reach towards the foothills of the Himalaya,[90][93][94] leading to erratic and less extensive floods that made inundation agriculture less sustainable. Aridification reduced the water supply enough to cause the civilisation's demise, and to scatter its population eastward.[95][96][97][note 3] As the monsoons kept shifting south, the floods grew too erratic for sustainable agricultural activities. The residents then migrated towards the Ganges basin in the east, where they established smaller villages and isolated farms. The small surplus produced in these small communities did not allow development of trade, and the cities died out.[98] The Indo-Aryan peoples migrated into the Indus River Valley during this period and began the Vedic age of India.[99] The Indus Valley Civilisation did not disappear suddenly and many elements of the civilization continued in later Indian subcontinent and Vedic cultures.[100]

Early evidence for Chinese millet agriculture is dated to around 7000 BC,[101] with the earliest evidence of cultivated rice found at Chengtoushan near the Yangtze River, dated to 6500 BC. Chengtoushan may also be the site of the first walled city in China.[102] This Neolithic Revolution gave rise to the Jiahu culture (7000 to 5800 BC).[103] Some scholars have suggested that the Jiahu symbols (6600 BC) are the earliest form of proto-writing in China.[104] However, it is likely that they should not be understood as writing itself, but as features of a lengthy period of sign-use which led eventually to a fully-fledged system of writing.[105] Excavation of a Peiligang culture site in Xinzheng county, Henan, found a community that flourished in 5500 to 4900 BC, with evidence of agriculture, constructed buildings, pottery, and burial of the dead.[106] With agriculture came increased population, the ability to store and redistribute crops, and the potential to support specialist craftsmen and administrators.[103] In late Neolithic times, the Yellow River valley began to establish itself as a center of Yangshao culture (5000 to 3000 BC), and the first villages were founded. Later, Yangshao culture was superseded by the Longshan culture, which was also centered on the Yellow River from about 3000 to 2000 BC.[107] The earliest bronze artifacts have been found in the Majiayao culture site (3100 to 2700 BC).[108][109]

Chinese civilization begins during the second phase of the Erlitou period (1900 to 1500 BC), with Erlitou considered the first state level society of East Asia.[110] There is considerable debate whether Erlitou sites correlate to the semi-legendary Xia dynasty. The Xia dynasty (2070 to 1600 BC) is the first dynasty to be described in ancient Chinese historical records such as the Bamboo Annals, first published more than a millennium later during the Western Zhou period. Although Xia is an important element in Chinese historiography, there is to date no contemporary written evidence to corroborate the dynasty. Erlitou saw an increase in bronze metallurgy and urbanization and was a rapidly growing regional center with palatial complexes that provide evidence for social stratification.[111] The Erlitou civilization is divided into four phases, each of roughly 50 years. During Phase I, covering 100 hectares (250 acres), Erlitou was a rapidly growing regional center with estimated population of several thousand[112] but not yet an urban civilization or capital.[113] Urbanization began in Phase II, expanding to 300 ha (740 acres) with a population around 11,000.[112] A palace area of 12 ha (30 acres) was demarcated by four roads. It contained the 150x50 m Palace 3, composed of three courtyards along a 150-meter axis, and Palace 5.[114] A bronze foundry was established to the south of the palatial complex that was controlled by the elite who lived in palaces.[115] The city reached its peak in Phase III, and may have had a population of around 24,000.[113] The palatial complex was surrounded by a two-meter-thick rammed-earth wall, and Palaces 1, 7, 8, 9 were built. The earthwork volume of rammed earth for the base of largest Palace 1 is 20,000 m³ at least.[116] Palaces 3 and 5 were abandoned and replaced by 4,200-square-kilometer (4.5×1010 sq ft) Palace 2 and Palace 4.[117] In Phase IV, the population decreased to around 20,000, but building continued. Palace 6 was built as an extension of Palace 2, and Palaces 10 and 11 were built. Phase IV overlaps with the Lower phase of the Erligang culture (1600–1450 BC). Around 1600 to 1560 BC, about 6 km northeast of Erlitou, Eligang cultural walled city was built at Yanshi,[117] which coincides with an increase in production of arrowheads at Erlitou.[112] This situation might indicate that the Yanshi City was competing for power and dominance with Erlitou.[112] Production of bronzes and other elite goods ceased at the end of Phase IV, at the same time as the Erligang city of Zhengzhou was established 85 km (53 mi) to the east. There is no evidence of destruction by fire or war, but, during the Upper Erligang phase (1450–1300 BC), all the palaces were abandoned, and Erlitou was reduced to a village of 30 ha (74 acres).[117]

The earliest traditional Chinese dynasty for which there is both archeological and written evidence is the Shang dynasty (1600 to 1046 BC). Shang sites have yielded the earliest known body of Chinese writing, the oracle bone script, mostly divinations inscribed on bones. These inscriptions provide critical insight into many topics from the politics, economy, and religious practices to the art and medicine of this early stage of Chinese civilization.[118] Some historians argue that Erlitou should be considered an early phase of the Shang dynasty. The U.S. National Gallery of Art defines the Chinese Bronze Age as the period between about 2000 and 771 BC; a period that begins with the Erlitou culture and ends abruptly with the disintegration of Western Zhou rule.[119] The Sanxingdui culture is another Chinese Bronze Age society, contemporaneous to the Shang dynasty, however they developed a different method of bronze-making from the Shang.[120]

The Norte Chico civilization proper is understood to have emerged around 3200 BC, as it is at that point that large-scale human settlement and communal construction across multiple sites becomes clearly apparent.[127] Since the early 21st century, it has been established as the oldest known civilization in the Americas. The civilization flourished at the confluence of three rivers, the Fortaleza, the Pativilca, and the Supe. These river valleys each have large clusters of sites. Further south, there are several associated sites along the Huaura River.[128] Notable settlements include the cities of Caral, the largest and most complex Preceramic site, and Aspero.[129] Norte Chico sites are known for their density of large sites with immense architecture.[130] Haas argues that the density of sites in such a small area is globally unique for a nascent civilization. During the third millennium BC, Norte Chico may have been the most densely populated area of the world (excepting, possibly, northern China).[131] The Supe, Pativilca, Fortaleza, and Huaura River valleys each have several related sites.

Norte Chico is unusual in that it completely lacked ceramics and apparently had almost no visual art. Nevertheless, the civilization exhibited impressive architectural feats, including large earthwork platform mounds and sunken circular plazas, and an advanced textile industry.[5][132] The platform mounds, as well as large stone warehouses, provide evidence for a stratified society and a centralized authority necessary to distribute resources such as cotton.[5] However, there is no evidence of warfare or defensive structures during this period.[131] Originally, it was theorized that, unlike other early civilizations, Norte Chico developed by relying on maritime food sources in place of a staple cereal. This hypothesis, the Maritime Foundation of Andean Civilization, is still hotly debated; however, most researches now agree that agriculture played a central role in the civilization's development while still acknowledging a strong supplemental reliance on maritime proteins.[133][134][135]

The Norte Chico chiefdoms were "almost certainly theocratic, though not brutally so", according to Mann. Construction areas show possible evidence of feasting, which would have included music and likely alcohol, suggesting an elite able to both mobilize and reward the population.[5] The degree of centralized authority is difficult to ascertain, but architectural construction patterns are indicative of an elite that, at least in certain places at certain times, wielded considerable power: while some of the monumental architecture was constructed incrementally, other buildings, such as the two main platform mounds at Caral,[136] appear to have been constructed in one or two intense construction phases.[131] As further evidence of centralized control, Haas points to remains of large stone warehouses found at Upaca, on the Pativilca, as emblematic of authorities able to control vital resources such as cotton.[5] Economic authority would have rested on the control of cotton and edible plants and associated trade relationships, with power centered on the inland sites. Haas tentatively suggests that the scope of this economic power base may have extended widely: there are only two confirmed shore sites in the Norte Chico (Aspero and Bandurria) and possibly two more, but cotton fishing nets and domesticated plants have been found up and down the Peruvian coast. It is possible that the major inland centers of Norte Chico were at the center of a broad regional trade network centered on these resources.[131]

Discover magazine, citing Shady, suggests a rich and varied trade life: "[Caral] exported its own products and those of Aspero to distant communities in exchange for exotic imports: Spondylus shells from the coast of Ecuador, rich dyes from the Andean highlands, hallucinogenicsnuff from the Amazon."[137] (Given the still limited extent of Norte Chico research, such claims should be treated circumspectly.) Other reports on Shady's work indicate Caral traded with communities in the jungle farther inland and, possibly, with people from the mountains.[138]

Leaders' ideological power was based on apparent access to deities and the supernatural.[131] Evidence regarding Norte Chico religion is limited: an image of the Staff God, a leering figure with a hood and fangs, has been found on a gourd dated to 2250 BC. The Staff God is a major deity of later Andean cultures, and Winifred Creamer suggests the find points to worship of common symbols of gods.[139][140] As with much other research at Norte Chico, the nature and significance of the find has been disputed by other researchers.[note 4] The act of architectural construction and maintenance may also have been a spiritual or religious experience: a process of communal exaltation and ceremony.[129] Shady has called Caral "the sacred city" (la ciudad sagrada[141]): socio-economic and political focus was on the temples, which were periodically remodeled, with major burnt offerings associated with the remodeling.[142]

The discovery of quipu, string-based recording devices, at Caral can be understood as a form of "proto-writing" at Norte Chico.[143] However, the exact use of quipu in this and later Andean cultures has been widely debated.[5] Additionally, the image of the Staff God has been found on a gourd dated to 2250 BC. The Staff God is a major deity of later Andean cultures. The presence of quipu and the commonality of religious symbols suggests a cultural link between Norte Chico and later Andean cultures.[139][140]

Circa 1800 BC, the Norte Chico civilization began to decline, with more powerful centers appearing to the south and north along the coast and to the east inside the belt of the Andes.[144] Pottery eventually developed in the Amazon Basin and spread to the Andean culture region around 2000 BC. The next major civilization to arise in the Andes would be the Chavín culture at Chavín de Huantar, located in the Andean highlands of the present-day Ancash Region. It is believed to have been built around 900 BC and was the religious and political center of the Chavín people.[145]

The Coxcatlan caves in the Valley of Tehuacán provide evidence for agriculture in components dated between 5000 and 3400 BC.[146] Similarly, sites such as Sipacate in Guatemala provide maize pollen samples dating to 3500 BC.[147] It is estimated that fully domesticated maize developed in Mesoamerica around 2700 BC.[148] Mesoamericans during this period likely divided their time between small hunting encampments and large temporary villages.[149] Around 1900 BC, the Mokaya domesticated one of the dozen species of cacao.[150][151] A Mokaya archaeological site provides evidence of cacao beverages dating to this time.[152] The Mokaya are also thought to have been among the first cultures in Mesoamerica to develop a hierarchical society. What would become the Olmec civilization had its roots in early farming cultures of Tabasco, which began around 5100 to 4600 BC.[153]

The emergence of the Olmec civilization has traditionally been dated to around 1600 to 1500 BC. Olmec features first emerged in the city of San Lorenzo Tenochtitlán, fully coalescing around 1400 BC. The rise of civilization was assisted by the local ecology of well-watered alluvial soil, as well as by the transportation network provided by the Coatzacoalcos River basin.[153] This environment encouraged a densely concentrated population, which in turn triggered the rise of an elite class and an associated demand for the production of the symbolic and sophisticated luxury artifacts that define Olmec culture.[154] Many of these luxury artifacts were made from materials such as jade, obsidian, and magnetite, which came from distant locations and suggest that early Olmec elites had access to an extensive trading network in Mesoamerica. The aspect of Olmec culture perhaps most familiar today is their artwork, particularly the Olmec colossal heads.[155] San Lorenzo was situated in the midst of a large agricultural area.[156] San Lorenzo seems to have been largely a ceremonial site, a town without city walls, centered in the midst of a widespread medium-to-large agricultural population. The ceremonial center and attendant buildings could have housed 5,500 while the entire area, including hinterlands, could have reached 13,000.[157] It is thought that while San Lorenzo controlled much or all of the Coatzacoalcos basin, areas to the east (such as the area where La Venta would rise to prominence) and north-northwest (such as the Tuxtla Mountains) were home to independent polities.[158] San Lorenzo was all but abandoned around 900 BC at about the same time that La Venta rose to prominence. A wholesale destruction of many San Lorenzo monuments occurred around 950 BC. A wholesale destruction of many San Lorenzo monuments also occurred circa 950 BCE, which may indicate an internal uprising or, less likely, an invasion.[159] The latest thinking, however, is that environmental changes may have been responsible for this shift in Olmec centers, with certain important rivers changing course.[160]

La Venta became the cultural capital of the Olmec concentration in the region until its abandonment around 400 BC; constructing monumental architectural achievements such as the Great Pyramid of La Venta.[155][153] It contained a “concentration of power,” as reflected by the sheer enormity of the architecture and the extreme value of the artifacts uncovered.[161] La Venta is perhaps the largest Olmec city and it was controlled and expanded by an extremely complex hierarchical system with a king, as the ruler and the elites below him. Priests had power and influence over life and death and likely great political sway as well. Unfortunately, not much is known about the political or social structure of the Olmec, though new dating techniques might, at some point, reveal more information about this elusive culture. It is possible that the signs of status exist in the artifacts recovered at the site such as depictions of feathered headdresses or of individuals wearing a mirror on their chest or forehead.[162] “High-status objects were a significant source of power in the La Venta polity political power, economic power, and ideological power. They were tools used by the elite to enhance and maintain rights to rulership.” [163] It has been estimated that La Venta would need to be supported by a population of at least 18,000 people during its principal occupation.[164] To add to the mystique of La Venta, the alluvial soil did not preserve skeletal remains, so it is difficult to observe differences in burials. However, colossal heads provide proof that the elite had some control over the lower classes, as their construction would have been extremely labor-intensive. “Other features similarly indicate that many laborers were involved.” [165] In addition, excavations over the years have discovered that different parts of the site were likely reserved for elites and other parts for non-elites. This segregation of the city indicates that there must have been social classes and therefore social inequality.[162] The exact cause of the decline of the Olmec culture is uncertain. Between 400 and 350 BC, the population in the eastern half of the Olmec heartland dropped precipitously.[166] This depopulation was probably the result of serious environmental changes that rendered the region unsuited for large groups of farmers, in particular changes to the riverine environment that the Olmec depended upon for agriculture, hunting and gathering, and transportation. These changes may have been triggered by tectonic upheavals or subsidence, or the silting up of rivers due to agricultural practices.[155][153] Within a few hundred years of the abandonment of the last Olmec cities, successor cultures became firmly established. The Tres Zapotes site, on the western edge of the Olmec heartland, continued to be occupied well past 400 BC, but without the hallmarks of the Olmec culture. This post-Olmec culture, often labeled Epi-Olmec, has features similar to those found at Izapa, some 550 km (330 miles) to the southeast.[167]

The Olmecs are sometimes referred to as the mother culture of Mesoamerica, as they were the first Mesoamerican civilization and laid many of the foundations for the civilizations that followed.[168] However, the causes and degree of Olmec influences on Mesoamerican cultures has been a subject of debate over many decades.[169] Practices introduced by the Olmec include ritual bloodletting and the Mesoamerican ballgame; hallmarks of subsequent Mesoamerican societies such as the Maya and Aztec.[168] Although the Mesoamerican writing system would fully develop later, early Olmec ceramics show representations that may be interpreted as codices.[153]

The following timeline shows the approximate dates of the emergence of civilization in the featured areas and the primary Neolithic cultures preceding them. It is important to note that the timeline is not indicative of the beginning of human habitation, or the start of a specific ethnic group; which often occurred significantly earlier than the emergence of civilization proper.

There is academic consensus that Classical Greece is the seminal culture which provided the foundation of modern Western culture, democracy, art, theatre, philosophy and science. For this reason it is known as the cradle of Western Civilization.[a] Along with Greece, Rome has sometimes been described as a birthplace or as the cradle of Western Civilization because of the role the city had in politics, republicanism, law, architecture, warfare and Western Christianity.[b]

^Geological research by a group led by Peter Clift investigated how the courses of rivers have changed in this region since 8000 years ago, to test whether climate or river reorganisations caused the decline of the Harappan. Using U-Pb dating of zircon sand grains they found that sediments typical of the Beas, Sutlej and Yamuna rivers (Himalayan tributaries of the Indus) are actually present in former Ghaggar-Hakra channels. However, sediment contributions from these glacial-fed rivers stopped at least by 10,000 years ago, well before the development of the Indus civilisation.[91]

^Tripathi et al. (2004) found that the isotopes of sediments carried by the Ghaggar-Hakra system over the last 20 thousand years do not come from the glaciated Higher Himalaya but have a sub-Himalayan source, and concluded that the river system was rain-fed. They also concluded that this contradicted the idea of a Harappan-time mighty "Sarasvati" river.[92]

^Broke:[97] "The story in Harappan India was somewhat different (see Figure 111.3). The Bronze Age village and urban societies of the Indus Valley are some-thing of an anomaly, in that archaeologists have found little indication of local defense and regional warfare. It would seem that the bountiful monsoon rainfall of the Early to Mid-Holocene had forged a condition of plenty for all, and that competitive energies were channeled into commerce rather than conflict. Scholars have long argued that these rains shaped the origins of the urban Harappan societies, which emerged from Neolithic villages around 2600 BC. It now appears that this rainfall began to slowly taper off in the third millennium, at just the point that the Harappan cities began to develop. Thus it seems that this "first urbanisation" in South Asia was the initial response of the Indus Valley peoples to the beginning of Late Holocene aridification. These cities were maintained for 300 to 400 years and then gradually abandoned as the Harappan peoples resettled in scattered villages in the eastern range of their territories, into the Punjab and the Ganges Valley....'
17 (footnote):
a)Liviu Giosan et al., "Fluvial Landscapes of the Harappan Civilization," PNAS, 102 (2012), E1688—E1694;
(b) Camilo Ponton, "Holocene Aridification of India," GRL 39 (2012), L03704;
(c) Harunur Rashid et al., "Late Glacial to Holocene Indian Summer Monsoon Variability Based upon Sediment Records Taken from the Bay of Bengal," Terrestrial, Atmospheric, and Oceanic Sciences 22 (2011), 215–28;
(d) Marco Madella and Dorian Q. Fuller, "Paleoecology and the Harappan Civilization of South Asia: A Reconsideration," Quaternary Science Reviews 25 (2006), 1283–301. Compare with the very different interpretations in Possehl, Gregory L. (2002), The Indus Civilization: A Contemporary Perspective, Rowman Altamira, pp. 237–245, ISBN978-0-7591-0172-2, and Michael Staubwasser et al., "Climate Change at the 4.2 ka BP Termination of the Indus Valley Civilization and Holocene South Asian Monsoon Variability," GRL 30 (2003), 1425. Bar-Matthews and Avner Ayalon, "Mid-Holocene Climate Variations."

^Krysztof Makowski, as reported by Mann (1491), suggests there is little evidence that Andean civilizations worshipped an overarching deity. The figure may have been carved by a later civilization onto an ancient gourd, as it was found in strata dating between 900 and 1300 AD.

^Carter, Robert A. and Philip, Graham Beyond the Ubaid: Transformation and Integration in the Late Prehistoric Societies of the Middle East (Studies in Ancient Oriental Civilization, Number 63) The Oriental Institute of the University of Chicago (2010) ISBN978-1-885923-66-0 p.2, at http://oi.uchicago.edu/research/pubs/catalog/saoc/saoc63.html; "Radiometric data suggest that the whole Southern Mesopotamian Ubaid period, including Ubaid 0 and 5, is of immense duration, spanning nearly three millennia from about 6500 to 3800 B.C".

^Pollock, Susan (1999). Ancient Mesopotamia: The Eden that Never Was. New York: Cambridge University Press. ISBN0-521-57334-3.

^Zvelebil, M. (1989). "On the transition to farming in Europe, or what was spreading with the Neolithic: a reply to Ammerman (1989)". Antiquity. 63 (239): 379–383. doi:10.1017/S0003598X00076110.

^Leick, Gwendolyn (2002), "Mesopotamia: The Invention of the City" (Penguin)

^Carter, Robert A. and Philip, Graham. 2010. 'Deconstructing the Ubaid' in Carter, Robert A. and Philip, Graham (eds.) Beyond the Ubaid: Transformation and Integration in the Late Prehistoric Societies of the Middle East. Chicago: The Oriental Institute of the University of Chicago. p. 2.

^Howells, William (1983). "Origins of the Chinese People: Interpretations of recent evidence". In Keightley, David N. The Origins of Chinese Civilization. University of California Press. pp. 297–319. ISBN978-0-520-04229-2.

^Coe (1967), p. 72. Alternatively, the mutilation of these monuments may be unrelated to the decline and abandonment of San Lorenzo. Some researchers believe that the mutilation had ritualistic aspects, particularly since most mutilated monuments were reburied in a row.